writing Float32Array to sd and read back ?

It depends on the size of the array I guess, and whether you want it human readable or not.

Text

// write
fs.writeFileSync("foo.txt", array.toString());
// read
array = new Float32Array(JSON.parse(fs.readFileSync("foo.txt")));

Binary

// write
fs.writeFileSync("foo.bin", E.toString(array.buffer));
// read
array = new Float32Array(E.toArrayBuffer(fs.readFileSync("foo.txt")));

For bigger arrays binary would be better, and for very big arrays you'd be looking at multiple save calls.